What are theses scabs underneath the chestnuts on his legs

[BarneyTheChestnutOne]

Found these scabs on my horses front legs this morning underneath his chestnuts. Anyone know what they are and what best to put on them?

https://scontent-lhr3-1.xx.fbcdn.ne...=45a155ed63d039e6ecd96c1e5faef05a&oe=5607A869

Thank You